BRUSSELS — Thirty-one people have been arrested in three countries in connection with the February theft of $50 million in diamonds at Brussels airport, the Brussels prosecutor’s office said.

Belgian police detained 24 people this morning in raids at 40 homes, mostly in Brussels, Anja Bijnens, a spokeswoman for the prosecutor’s office, told reporters Wednesday in the Belgian capital. Six people were arrested yesterday in Switzerland and one in France, she said.

Some of the stolen diamonds were found in Switzerland and a “large amount” of money was recovered in Belgium, Bijnens said. More than 200 police officers took part in the Belgian operation, she said.

In the Feb. 18 theft, armed gunmen took the gems at Brussels airport as they were being loaded onto a plane bound for Switzerland.

The eight masked men with machines guns and in police clothing breached the perimeter at the airport in two black vehicles with flashing blue lights and drove up to a Helvetic Air plane operated by Swiss International Air Lines Ltd.

They stole at least 120 packets of diamonds that had just been transferred from a Brink’s Co. security van into the cargo hold.

“It was very well organized, very swift, efficient, and well planned,” Jan Van der Cruysse, a spokesman for the airport, said at the time. The thieves stopped at the plane for just three minutes and the whole operation took just over 10 minutes, he said.

Brussels airport is 42 kilometers (26 miles) from Antwerp, Belgium’s second-largest city and the biggest trading hub for rough diamonds.